MODELING AND STATIC ANALYSIS OF SINGLE CYLINDER PETROL ENGINE

PISTON

A V Hari Babu1*

, G Pandu Ranga Swamy2, D R Subba Rao

3 , M Sudhakar Reddy

4, S

Ramesh Kumar Babu5,

1. Associate Professor & Head of ME, SVR Engg College, Nandyal.

2, 3, 4, 5 Assistant Professor, SVR Engg College, Nandyal

*Corresponding Author:A V Hari Babu,

When the combustion of fuel takes place in petrol engine cylinder, high temperature and

pressure will be developed because the engine will run at high speed and at high loads. Generally

piston is made of Al Alloy which is a crucial part in internal combustion engines. This report

deals the modeling and analysis of petrol engine piston is done by using cast iron and

compositions of aluminum alloy. Initially structural analysis was performed on cast iron, Al

Alloy.

The objective of this project report is to model and analyze the petrol engine piston. In

this project the geometric model of piston is generated in CATIA V5 software. The geometrical

model is cleaned and meshed in to finite elements by using HyperMesh12 software. Finite

Element model was solved using ABAQUS software for stress and displacement as per the

calculated load.

Keywards: single cylinder petrol engine piston, CATIA, HYPERMESH and ABAQUS.

INTRODUCTION

A piston is a cylindrical engine component that slides back and forth in the cylinder bore

by forces produced during the combustion process. The piston acts is a movable end of the

combustion chamber .The stationary end of the combustion chamber is the cylinder head. Pistons

are commonly made of a cast aluminum alloy for excellent and light weight thermal conductivity

is the ability of a material to conduct and transfer heat. Aluminum expands when heated and

proper clearance must be provided to maintain free piston movements in the cylinder bore.

Insufficient clearance can cause the piston to seize in the cylinder. Excessive clearance can cause

a loss of compression and an increase in piston noise. a complete illustration of that piston and its

parts are shown below.

Fig 1.1 Piston feature

Piston features include the piston head, piston pin bore, skirt ring grooves, ring lands, and

piston rings. The piston head is the top surface (closes to the cylinder head) of the piston which

is subjected to tremendous forces and heat during normal engine operation.

1.1 Type of pistons

There are essentially two types of piston used in todays in automotive engine.

1.1.1 Mono piston

By far the most common, and the one used in all passenger car engines, is the mono

piston .As the name suggests, the piston comprise of a single component, which is usually made

from aluminium. The upper part of the piston that supports the combustion force and holds the

piston rings is called the Crown. The lower part of the piston that supports the lateral forces

against the inner walls is called Skirt the piston is linked to the connecting rod via the wrist pin

on which both components are hinged. An example of a mono piston assembly can be seen in

figure in below

Fig 1.2 mono piston assembly

1.1.2 Articulated piston

In some heavy duty diesel engines, due to extremely high combustion temperatures and

pressures, it is desirable to have a stainless steel crown section. An aluminum skirt is still

preferable due to its low weight and elasticity. Two components of different materials cannot be

rigid joined together in the position, as their differing coefficients of expansion would lead to

failure. Instead, articulated pistons comprise a stain less steel crown and an aluminum skirt

which are separate components and are hinged separately on the wrist pin. An example of an

articulated piston assembly can be shown in figure

Fig 1.3- articulated piston assembly

The piston motion equations are traditional Newton’s law of vertical and lateral motion

and rotation applied to the piston in standard manner the forces acting on a piston are

exemplified in figure these forces and movements come from interactions of the piston with the

liner, rings, wristpin, cylinder pressure and inertia.

Fig 1.4-forces & movements acting on the piston

2. DESIGN OF PISTION

Design considerations for a piston

Piston should have enormous strength to withstand high gas pressure and inertia forces in

addition to disperse the heat of combustion quickly to the cylinder walls. It should provide

sufficient bearing area to prevent undue wear in addition to having sufficient support for the

piston pin. And also it should have sufficient rigid construction to withstand thermal and

mechanical distortion in addition to it acts as effective sealing to the gases not to escaping from

combustion chamber.

Engine specification

The Engine selected for this work is a single cylinder four stroke air cooled 100cc proto

type petrol engine. The main parameter shows in the table below table 1

Engine

Type 4-stroke,air cooled, single cylinder

Number of cylinders Single cylinder

Bore 41 mm

Stroke 75 mm

Length of connecting rod 150 mm

Compression ratio 8.4

Fuel consumption 87 kmpl (under standard condition)

Performance Maximum power 6.03kw@7500 rpm

Maximum torque 8.05n-m@5500 rpm

Transmission Clutch Wet multi disc type

Transmission 4-speed,constant mesh type

Gear shift pattern All down foot shift

Dimensions Overall length 1925mm

Overall height 1030mm

Wheel base 1215mm

Ground clearance 150mm

Kerb weight with full tank 109kg

Capacity Fuel tank 9.3 liters including 2.2liters reserve

Table 1: Engine specification

s/no Description Nomenclature Value in mm

1 Thickness of piston head tH 7

2 Radial width of piston ring 2

3 Axial thickness of piston ring 1

4 Width of top land 4

5 Width of ring land 2

6 Thickness of piston barrel at the top end 5

7 Length of skirt 18

8 Length of piston pin in the connecting rod bushing 20

9 Piston pin diameter 10

10 Radial width of oil ring 3

11 Axial thickness of piston t5 2.5

Table 2 Piston specification

Fig: Piston cut section

CATIA V5 Workbenches

CATIA V5 serves the basic design tasks by providing different workbenches. A

workbench is defined as a specified environment consisting of a set of tools that allows the

user to perform specific design task. The basic workbenches in CATIA -V5 are

1. Part design

2. Wire frame

3. Surface design

4. Assembly design

5. Drafting

6. Generative sheet metal design

7. DMU Kinematics

Getting Started with HyperMesh

In this tutorial, you will explore the basic concepts of the user interface of Hyper Mesh.

Tools

The Hyper Mesh interface contains several areas. Each is described below.

Hyper Mesh Graphical Interface

Starting Hyper Mesh

To start Hyper Mesh on a PC, go to Start > Programs > Altair Hyper Works > Altair

Hype Mesh

To start HyperMesh on UNIX, perform the following steps:

Go to your operating system prompt.

Enter the full path of the Hyper Mesh script (e.g., <altair_home>\altair\scripts\hm) and press

the ENTER key.

Or

Type in a pre-defined alias that you or a systems administrator has created in the user .alias

or .cshrc file in the user home directory.

Start Directory

By default, Hyper Mesh uses a "start directory" for files. Hyper Mesh reads and writes a number

of files from the start

Directory:

At start up, Hyper Mesh reads configuration files (hm.mac, hmmenu.set, etc.).

Upon closing, Hyper Mesh writes out a command history file (command.cmf) and a menu

settings file (hmmenu.set).

By default, Hyper Mesh will read from/write to this directory for any open, save, save as,

import, or export functionality.

Image files (.jpg) created using the F6 key are saved to the start directory.

To determine the start directory on Windows, perform the following steps:

1. Right-click the Hyper Mesh icon.

2. Go to Properties.

3. On the Shortcut tab, view the path in the Start In field.

On UNIX, the start directory is determined by the following:

Location in which you typed the command to run Hyper Mesh

Your "home" directory if configuration files are not found in the start directory

HyperMesh Help

To obtain help for a particular feature, go to the Help menu and select Hyper Mesh and

Batch Mesher. The help is organized by product and contains the following types of

information:

How to use individual functions

Notes on interfacing Hyper Mesh with external data types

Tutorials

Programming guides

Model Files

All files referenced in the Hyper Mesh tutorials are located in the

<install_directory>\tutorials\hm\ directory unless otherwise noted.

Opening and Saving Files

In this tutorial, you will learn how to:

Open a Hyper Mesh file

Import a file into a current Hyper Mesh session

Save the Hyper Mesh session as a Hyper Mesh model file

Export all the geometry to an IGES file

Export all the mesh data to an OptiStruct input file

Delete all data from the current Hyper Mesh session

Import an IGES file

Import an OptiStruct file to the current Hyper Mesh session

Starting ABAQUS

When you create a model and analyze it, ABAQUS/CAE generates a set of files

containing the definition of your model, the analysis input, and the results of the analysis. In

addition, ABAQUS/CAE and ABAQUS/Viewer generate replay files that reflect all your

interactions with the application. Consequently, before you run either product, you should move

to a directory where you have permission to create files.

FINITE ELEMENTS ANALYSIS

Finite Element Analysis (FEA) is a computer-based numerical technique for calculating

the strength and behavior of engineering structures. It can be used to calculate deflection, stress,

vibration, buckling behavior and many other phenomena .It can be used to analyze elastic

deformation or permanently bent out of shape plastic deformation. The computer is required

because of the astronomical number of calculations needed to analyze a large structure. The

power and low cost of modern computers has made finite element analysis available to many

disciplines and companies.

Failure Modes

1. Static loads lead to stresses exceeding yield over a significant region.

2. Loads on bolts, rivets, spot-welds, stitch-welds, fillet-welds, bevel-welds, full penetration-

welds, adhesives, nails, tie-rods, links or other connection devices are too high.

3. Strains reach fracture levels in brittle materials.

4. Surface strains cause damage to protective coatings.

5. Buckling of components leads to local damage or progressive collapse.

6. Combined bending and compression leads to excessive stress and failure.

7. Fatigue or sudden fracture is reached.

8. Vibration frequencies are located where applied loading causes damage

PROCESS METHODOLOGY

The geometrical model has been created in CATIA V6. 3D model of piston is imported

into the HyperMesh for preprocessing. Preprocessing of model consist of meshing, selection of

material properties, creation of load collectors and apply boundary conditions on model. Then

model is exported to ABAQUS for solving problem. Results of solution plotted in ABAQUS

which is well known postprocessor of Hyper Works software

Methodology flow chart

Creating geometry in CATIA

1. Open CATIA V5 Software.

2. Go to start, select Mechanical Design and select Part Design.

3. Select one plane from specification tree and select sketcher.

4. Draw the cross sectional area of the piston as show in the following figure.

Piston cross section view

5. Give the constraints (dimensions) as per the piston specification table and exit from the

sketching workbench.

6. Select shaft tool for to revolve the sketch in 360o about its vertical axis.

Revolved piston isotropic view

7. Create a plane by selection offset from plane option

8. Draw a rectangle by selecting newly created plane and exit from sketcher

9. Select pocket option and select that rectangle box with a depth of 3 mm.

Rectangle piston isotropic view

10. Create one hole with diameter of 10 mm on the piston as shown in the following figure

Piston pin hole isotropic view

11. Draw two circles with diameter 14 mm and 10 mm and pad it.

12. Select pocket-1, pocket-2 and pad-1 from specification tree then click on mirror tool by

selecting mid plane as a reference for to mirror the object.

13. Save the model with name Piston

Piston views

Geometry file importing to Hypermesh

1. Open HyperMesh software select ABAQUS profile

2. Go to import option select geometry, browse piston geometry file which is created in

CATIA

3. Click on solid shape option and topo

4. Save the file with name piston

Geometry clean up and meshing

1. Create a centre node with arc option by selecting piston outer arc

2. Cut the piston into four quarter part by selecting trim with plane option

3. Delete three quarter parts and you will get a quarter part of a piston as shown in following

figure

Piston quarter cut

4. Trim the geometry bi using surface option and by line sweep option so that we can get six

face volume blocks

5. Go to 3-d page select solid map, select one volume option give the element size as 1 pick

the six face volume click on mesh

6. Repeat step 5 till whole quarter part of piston get meshed

7. A mapped mesh of mixed elements of 8 node hexahedral and 6 node prism elements will

appear

8. Go to tool page select reflect option

9. Reflect all elements one time about vertical axis and second time with horizontal axis

10. Select edge option from tool page Give connectivity between all elements by choosing

equivalence option

11. A complete meshed model shown in following figure

Complete Mapped mesh model

12. Save the file with name complete mesh

This FEA model consist of mixed elements of 8 node hexahedral, 6 node prism, 4

node quad element and 3 node tria elements

S.

no

Name of the element No.of

elements

1 Hexahedral 8 node 22576

2 Prism 6 node (Penta 6 268

node)

3 Quad 4 node 1632

4 Tria 3 node 8

Total 24484

Table: 4 No of Elements in FEA modal

Material selection

In this report three materials are selected for to do a comparison for to get best

material selection for the piston of a proto type petrol engine. Those three materials are

1. Aluminium alloy Al-2681

2. Cast iron

1. Aluminium alloy Al-2681

Aluminium / Aluminum alloys have high ductility and corrosion resistance. At

subzero temperatures, their strength can be increased. However, their strength can be reduced at

high temperatures of about 200-250°C. Aluminium / Aluminum 2618 alloy is an age harden able

alloy containing magnesium and copper.

The following table shows the chemical composition of Aluminium / Aluminum 2618 alloy.

Element Contents (%)

Aluminium /

Aluminum, Al 93.7

Copper, Cu 2.30

Magnesium, Mg 1.60

Iron, Fe 1.1

Nickel, Ni 1.0

Silicon, Si 0.18

Titanium, Ti 0.07

Table: 5 Chemical compositions of AL-2681

The physical properties of the Aluminium / Aluminum 2618 alloy are tabulated below.7

Properties Metric

Density 2.768 g/cm3

Melting point 5100C

Table: 6 Physical properties of AL-2681

The mechanical properties of the Aluminium / Aluminum 2618 alloy are outlined in the

following table.8

Properties Metric

Ultimate strength 440 Mpa

Yield strength 370 Mpa

Shear strength 260 Mpa

Fatigue strength 125 Mpa

Elastic modulus 70-80 GPa

Poisson's ratio 0.33

Elongation 10%

Table: 7 Mechanical properties of AL-2681

2. Cast iron

An alloy of iron that contains 2 to 4 percent carbon, along with varying amounts of

silicon and manganese and traces of impurities such as sulfur and phosphorus. It is made by

reducing iron ore in a blast furnace. The liquid iron is cast, or poured and hardened, into crude

ingots called pigs, and the pigs are subsequently re-melted along with scrap and alloying

elements in cupola furnaces and recast into molds for producing a variety of products.

Most cast iron is either so-called gray iron or white iron, the colours shown by fracture.

Gray iron contains more silicon and is less hard and more machinable than white iron

Properties Metric

Density 6.8 gm/cm3

Young’s modulus 110 Gpa

Melting point 1090oC

Ultimate strength 350 Mpa

Yield strength 240 Mpa

Table: 8 Mechanical properties of Cast iron

Creating load collectors and applying boundary condition 1. Create load collector by using load collector option from tool bars

2. Give name as fixed, select colour green and image card as initial condition

3. Go to analysis page select constraints select all node at the pin hole of the piston as

shown in following figure

4. Select all DOF click create

5. Create load collector by using load collector option from tool bars

6. Give name as pressure, select colour red and image card as history condition

7. Go to analysis page select pressure, select elements top surface at the piston head and

give magnitude as 12.5 MPa, shown in following figure

8. Go to analysis page select load steps

9. Give name as static

10. Click on load cols select fixed and pressure

11. Click on create and also on edit

12. Select step parameters, perturbation, analysis processor static, load_op_options,

Boundary_op and D load_op select return

13. Save the file

Exporting to ABAQUS

1. Select export option from tool bar

2. Select export solver deck

3. Set path and name to the file with extension of .inp

4. Click export

5. Open ABAQUS and set working directory

6. Import Hyper Mesh export file and delete model-1

7. Right click on job and select create job-1

8. Right click on job-1 and select submit

9. Wait till it complete the solving after that save the model

Plotting results in ABAQUS

1. After completing the solving right click on job-1 select results

2. Select plot contours on deformation option from tool bar

3. Go to field output and select stress, select Misess

4. Go to field output and select stress, select Max-principle.

5. Go to field output and select spatial displacement at nodes, select magnitude

6. Save the results and exit

RESULTS AND DISCUSSIONS:

The following FEA results are got from ABAQUS software, when the piston head

experience 12.5 MPa pressure inside the cylinder.

Fig: 1 Von-Mises stress distribution in Al-2618 material piston

The above figure 1 shows Mises stress distribution in an Al-2618 material piston. The

maximum stress is 165.4 MPa and minimum stress is 0.78 MPa,

Fig:2 Von-Mises stress distribution in Cast iron material piston

The above figure 2 shows Mises stress distribution in a Cast iron material piston. The

maximum stress is 169.3 MPa and minimum stress is 1.153 MPa,

Fig: 3 Maximum principle stress distribution in Al-2618 material piston

The above figure 3 shows Maximum principle stress distribution in an Al-2618 material piston.

The maximum stress is 62.12 MPa and minimum stress is -18.47 MPa,.

Fig: 4 Maximum principle stress distribution in Cast iron material piston

The above figure 4 shows Maximum principle stress distribution in a Cast iron material

piston. The maximum stress is 61.78 MPa and minimum stress is -12.25 Mpa. As comparing the

AL-2618 material the maximum principle stress value is decreased in cast iron material by 0.35

MPa

Fig: 5 Deformation in Al-2618 material piston

The above figure 5 shows deformation in an Al-2618 material piston. The maximum

deformation is 0.0402 mm,

Fig: 6 Deformation in Cast iron material piston

The above figure 6 shows deformation in a Cast iron material piston. The maximum

deformation is 0.02715 mm. As comparing the AL-2618 material the maximum deformation

value is decreased in cast iron material by 0.01305 mm.

The following table shows the result comparison between two materials

s.no Materia

l name

Young’s

modulu

s (MPa)

Poisson

’s ratio

Density

(g/mm3

)

Mass

(Gms

)

Von Mises

Stress

(MPa)

Max-

Principle

stress

(MPa)

Deforma

tion(mm

)

1 Al-2618 73.7x103 0.33

0.0027

6 51.9 165.4 62.12 0.04020

2

Cast

iron 110 x103 0.22

0.0068

0 127.5 169.3 61.78 0.02715

Table: 9 FEA result comparison between two materials

CONCLUSION

Compared results based on AL Alloy and cast iron (Al-2618, Cast Iron). AL alloy gives best

results. . Because the stresses induced in the piston reduced. Hence the prepared piston with

AL-Alloy specimen show better results than the normal Cast Iron.

REFERENCE

P.carvalheira,p.Goncalves FEA of two engine pistons made of al cast alloy A390 and Ductile

iron 65-45-12 under service conditions.

V. Ucar, A. Ozel, “Use of the finite element technique to analyze the influence of coating

materials, material phase state and the purity on the level of the developed thermal stresses in

plasma coating systems under thermal loading conditions”, Surface and Coatings

Technology, Vol. 142 144, 2001, pp. 950-953

R. Ravi Raja Malarvannan1, P. Vignesh2 “Experimental Investigation And Analysis Of

Piston By Using Composite Materials,” Department Of Manufacturing Engineering, College

Of Engineering Guindy. Vol 04, Article K100; November 2013.

Hongyuan Zhang, Xingguo Ma, Shuangliang Ge “Modeling And Transient Dynamics

Analysis To a new Type Of Engine Piston” 2013.

Ghodake A. P. Patil K.N. “Piston Design And Analysis By Cae Tools” Department Of

Mechanical Engineering, Snd Coe & Rc Yeola, Nashik, India Iosr Journal Of Engineering

(Iosrjen) Issn: 2250-3021 Isbn: 2878-8719 Pp 33-36 National Symposium On Engineering

And Research

Ch.Venkata Rajam, P.V.K.Murthy, M.V.S.Murali Krishna, G.M.Prasada Rao “Design

Analysis And Optimization Of Piston Using Catia And Ansys” International Journal Of

Innovative Research In Engineering & Science Issn 2319-5665(January2013, Issue 2

Volume1)